Deterministic stochastic resonance in a Rössler oscillator.

We discuss the characteristics of stochastic resonancelike behavior observed in a deterministic system. If a periodically forced Rössler oscillator strays from the phase locking state, it exhibits the intermittent behavior known as phase slips. When the periodic force is modulated by a weak signal, the phase slips synchronize with the weak signal statistically. We numerically demonstrate, in terms of interslip intervals and signal to noise ratio, that the maximum synchronization can be achieved with the optimum intensity of chaotic fluctuations. It is shown that the stochastic resonancelike behavior can be observed regardless of the choice of parameters. The frequency dependence of the signal indicates that there is an optimum frequency for the maximum resonance. The phase slip rate is derived based on the fact that the phase slips are caused by a boundary crisis caused by an unstable-unstable pair bifurcation. The interslip distributions obtained from the derived slip rate and the approximation theory of the time-dependent Poisson process agree with those obtained by numerical simulations. In addition, the maximum enhancement of a weak signal is shown to be achieved by adjusting the chaotic fluctuations even if a signal becomes mixed with noise.